Methods to size a gastric pouch

ABSTRACT

Methods to size a gastric pouch. In at least one embodiment for measuring the size of a gastric pouch of the present disclosure, the method comprises the steps of introducing a catheter into an esophagus, the catheter comprising an outer elongate tube, an inner elongate tube disposed within the outer elongate tube, a proximal balloon attached to the outer elongate tube, a distal balloon having a first end attached to the outer elongate tube and a second end attached to the inner elongate tube, at least two detection electrodes positioned on the outer elongate tube between at least two excitation electrodes, and a pressure transducer positioned on the outer elongate tube, locating the gastroesophageal junction using the proximal balloon, adjusting the distal balloon axially to a desired balloon length, injecting a fluid into the distal balloon to extend the distal balloon circumferentially, and determining a size variable of the gastric pouch.

PRIORITY

The present patent application is related to, claims the prioritybenefit of, and is a U.S. Divisonal patent application of, U.S.Nonprovisional patent application Ser. No. 12/211,303, filed Sep. 16,2008 and issued as U.S. Pat. No. 7,963,929 with an issue date of Jun.21, 2011, which is related to, and claims the priority benefit of, U.S.Provisional Patent Application Ser. No. 60/974,374, filed Sep. 21, 2007,the entire contents of which are hereby incorporated by reference intheir entirety into this disclosure.

BACKGROUND

In order to treat obesity, conventional surgical procedures involveattempts to either (1) restrict food intake into the body via arestrictive bariatric procedure or (2) divert the peristalsis of aperson's normal food intake past the small intestine to decrease caloricabsorption via a malabsorptive bariatric procedure. There also existscombined procedures in which both of the aforementioned techniques areemployed jointly.

Restrictive procedures have encountered more success than malabsorptiveones, with the latter resulting in severe nutritional deficiencies insome cases. In restrictive procedures, the goal is to construct apassageway from the upper portion of the stomach to the lower portion,thereby preventing the stomach from storing large amounts of food andslowing the passage of food from the esophagus to the small intestine.Such a surgery results in the formation of a small pouch on the superiorportion of the stomach near the gastroesophageal junction. In thebeginning, the formed pouch holds approximately one ounce of food, butlater distends to store two to three ounces. The lower outlet of thepouch is approximately one-half inch in diameter or smaller. The pouchdiverts the passage of food to the lower portion of the stomach, thusavoiding storage of food in the stomach itself. When the pouch is full,it stimulates a feeling of satiation as well.

Purely restrictive operations for obesity include adjustable gastricbanding (AGB) and vertical banded gastroplasty (VBG). These processes donot affect the digestive process. In AGB, a hollow silicone rubber bandis placed around the stomach near its upper end, creating a small pouchand a narrow passageway into the rest of the stomach. The band is theninflated with a saline solution through a tube that connects the band toan access port located subcutaneously. It can be tightened or loosenedover time to modify the size of the passage by increasing or decreasingthe quantity of saline solution. Similarly, VBG utilizes rubber bandsbut also uses staples to create a small stomach pouch. The procedureinvolves puncturing the stomach to create a pouch that is not subject tothe manual regulation observed in AGB.

In a malabsorptive bariatric procedure, an intestinal bypass isperformed resulting in the exclusion of almost all of the smallintestine from the digestive tract so that the patient absorbs a smalleramount of calories and nutrients. An example of a malabsorptiveprocedure is biliopancreatic diversion (BPD), in which aboutthree-fourths of the stomach is removed in order to restrict food intakeand decrease stomach acid production. The effect of this procedure is toalter the anatomy of the small intestine via the formation of analimentary limb that diverts the passage of food past the first portionof the small intestine, including the duodenum and jejunum, and therebyprevents some of the bile and pancreatic juices from digesting some ofthe ingested food.

Combined operations are the most common bariatric procedures performedtoday. They restrict both food intake and the amount of calories andnutrients the body absorbs. An example of a combined procedure is theExtended (Distal) Roux-en-Y Gastric Bypass in which a stapling creates asmall (15 to 20 cc) stomach pouch completely separated from theremainder of the stomach. The remainder of the stomach is not removed.The outlet from this newly formed pouch empties directly into the lowerportion of the jejunum, which decreases caloric absorption. Thisconnection is made by dividing the small intestine just below theduodenum and attaching the lower portion of the jejunum to the newlyformed stomach pouch. The other end is connected into the side of theRoux limb of the intestine creating the “Y” shape that gives thetechnique its name.

There is ample evidence that gastric pouch size is a key factorinfluencing weight loss after bariatric surgery. There have been reportsof an inverse relation between pouch size and excess weight loss; inother words, a smaller pouch will lead to greater weight loss. There isa limit to the minimum dimension, however, for health and safetyreasons. Efforts to standardize small pouch size for all patients areimportant to the success of surgical therapy for morbid obesity.

The size of the pouch is important to the outcome of the procedure forAGB, VBG, or Roux-en-Y. Indeed, the AGB patients require a weekly visitto adjust the size of the pouch for maximum efficacy. Generally, therehas been an inability to measure accurately and reproducibly the size ofthe gastric pouch, although a number of attempts have been made. Someresearchers have used intraoperative measurement of pouch size withinjected saline through a nasogastric tube before stapling of thestomach. Balloon catheters attached to a nasogastric tube and inflatedwith fluid have also been used. Nevertheless, the vast majority ofbariatric surgeons currently estimate the pouch size using a visualestimate (i.e., transecting the stomach a specific distance for thegastroesophageal junction or between the second and third branches ofthe left gastric arterial cascade). Postoperatively, radiographicmethods have been employed to approximate a three-dimensional pouch sizevolume from a two-dimensional filled contrast pouch.

The most commonly used method for studying the size and distensibilityof hollow organs includes a balloon mounted on a catheter with impedanceelectrodes for measurement of the cross-sectional area in the middle ofthe balloon along with the balloon pressure (referred to as impedanceplanimetry). The distensibility of the organ is derived from computationof parameters such as tension, strain, cross-sectional areadistensibility, and compliance (ΔCSA/ΔP) where ΔCSA denotes the changein cross-sectional area and ΔP denotes the change in pressure. Tensionis computed using Laplace's law in the form T=ΔP*r where ΔP and r arethe transmural pressure and the luminal radius of the organ,respectively.

BRIEF SUMMARY

Various embodiments of devices, methods, and systems for measuring thesize of a gastric pouch are disclosed herein. At least some embodimentsinclude a catheter comprising an outer elongate tube having a proximalend and a distal end, an inner elongate tube having a proximal end and adistal end, the inner elongate tube positioned at least partially withinthe outer elongate tube such that the inner elongate tube is capable ofsliding within the outer elongate tube, a proximal balloon surroundingat least a portion of the outer elongate tube near the distal end of theouter elongate tube, the proximal balloon having a first end attached tothe outer elongate tube and a second end attached to the outer elongatetube, a distal balloon surrounding a portion of the outer elongate tubedistal to the proximal balloon, the distal balloon having a first endattached to the outer elongate tube and a second end attached to theinner elongate tube, at least two excitation electrodes attached to theportion of the outer elongate tube surrounded by the distal balloon, theat least two excitation electrodes capable of attachment to a powersource, at least two detection electrodes attached to the outer elongatetube relative to the at least two excitation electrodes, the at leasttwo detection electrodes capable of attachment to a processor, a firstpressure transducer attached to the portion of the outer elongate tubesurrounded by the proximal balloon, and a second pressure transducerattached to the portion of the outer elongate tube surrounded by thedistal balloon. Such embodiments may include three, four, or five ormore detection electrodes. Certain embodiments further comprise a firstfluid passageway for injecting fluid into the proximal balloon and asecond fluid passageway for injecting fluid into the distal balloon.

At least some embodiments include an inner elongate tube comprising atleast one gradation at or near the proximal end of the inner elongatetube. Many of such embodiments include at least two gradationspositioned on the inner elongate tube a predetermined distance apart. Insome embodiments, the gradations comprise notches on the inner elongatetube and the outer elongate tube has a latch at or near the proximal endof the outer elongate tube, the latch being configured to engage one ormore of the notches such that the inner elongate tube and the outerelongate tube are reversibly fastened.

In some embodiments, the outer elongate tube comprises a flexibleportion near the distal end of the outer elongate tube, the flexibleportion capable of being bent into a curve, and the inner elongate tubeis flexible such that the inner elongate tube is capable of slidingwithin the flexible portion of the outer elongate tube when the flexibleportion is bent into a curve. In other embodiments, the outer elongatetube comprises a curved portion near the distal end of the outerelongate tube, and the inner elongate tube is flexible such that theinner elongate tube is capable of sliding within the curved portion ofthe outer elongate tube.

Certain embodiments disclosed herein include a system for measuring thesize of a gastric pouch, comprising a catheter having an outer elongatetube, an inner elongate tube positioned at least partially within theouter elongate tube, a proximal balloon attached to the outer elongatetube, a distal balloon having a first end attached to the outer elongatetube and a second end attached to the inner elongate tube, at least twodetection electrodes positioned on the outer elongate tube relative toat least two excitation electrodes, and a pressure transducer positionedon the outer elongate tube, a first processor operatively connected tothe at least two detection electrodes, the first processor being capableof collecting conductance data and determining a size variable, and apower source operatively connected to the at least two excitationelectrodes, wherein the power source is capable of providing current tothe excitation electrodes. In at least some embodiments, the catheterfurther comprises a first fluid passageway for injecting fluid into theproximal balloon and a second fluid passageway for injecting fluid intothe distal balloon. In some embodiments, the first processor isoperatively connected to the pressure transducer, the first processorbeing capable of collecting pressure data. However, in otherembodiments, there is a second processor operatively connected to thepressure transducer, the second processor being capable of collectingpressure data. In certain embodiments, the size variable comprises anapproximate cross-sectional area of the gastric pouch. In others, thesize variable comprises an approximate volume of the gastric pouch.

In some embodiments, the system further comprises a fluid sourceoperatively connected to the catheter, such that a fluid from the fluidsource can be injected into the proximal balloon or the distal balloon.In certain of those embodiments, the fluid source comprises a syringe.

The system may also further comprise a graphical display screen fordisplaying pressure data or size variables.

Other embodiments include a method for measuring the size of a gastricpouch, the method comprising the steps of introducing a catheter into anesophagus, the catheter comprising an outer elongate tube, an innerelongate tube disposed within the outer elongate tube, a proximalballoon attached to the outer elongate tube, a distal balloon having afirst end attached to the outer elongate tube and a second end attachedto the inner elongate tube, at least two detection electrodes positionedon the outer elongate tube between at least two excitation electrodes,and a pressure transducer positioned on the outer elongate tube;locating the gastroesophageal junction using the proximal balloon;adjusting the distal balloon axially to a desired balloon length;injecting a fluid into the distal balloon to extend the distal ballooncircumferentially; and determining a size variable of the gastric pouch.In certain embodiments, the step of locating the gastroesophagealjunction using the proximal balloon comprises the steps of positioningthe proximal balloon at a location at or near the gastroesophagealjunction, injecting fluid into the proximal balloon to extend theproximal balloon circumferentially, and measuring a pressure inside theproximal balloon. The step of adjusting the distal balloon axially to adesired balloon length may comprise the step of extending the distalballoon axially by sliding the inner elongate tube within the outerelongate tube. The step of adjusting the distal balloon axially to adesired balloon length may further comprise the step of sliding theinner elongate tube within the outer elongate tube until a gradation onthe inner elongate tube is aligned with the proximal end of the outerelongate tube. In some embodiments, the step of adjusting the distalballoon axially to a desired balloon length further comprises the stepof sliding the inner elongate tube within the outer elongate tube untila gradation on the inner elongate tube is engaged by a latch on theproximal end of the outer elongate tube, such that the inner elongatetube and the outer elongate tube are reversibly fastened.

The step of adjusting the distal balloon axially to a desired balloonlength may comprise the step of shortening the distal balloon axially bysliding the inner elongate tube within the outer elongate tube. The stepof adjusting the distal balloon axially to a desired balloon length mayfurther comprises the step of sliding the inner elongate tube within theouter elongate tube until a gradation on the inner elongate tube isaligned with the proximal end of the outer elongate tube. In someembodiments, the step of adjusting the distal balloon axially to adesired balloon length further comprises the step of sliding the innerelongate tube within the outer elongate tube until a gradation on theinner elongate tube is engaged by a latch on the proximal end of theouter elongate tube, such that the inner elongate tube and the outerelongate tube are reversibly fastened.

In certain embodiments, the fluid injected into the distal ballooncomprises saline solution.

The step of determining a size variable of the gastric pouch maycomprise the step of determining a pressure inside the distal balloon.In addition, the step of determining a size variable of the gastricpouch may comprise the step of determining a cross-sectional area of aportion of the distal balloon. The step of determining a size variableof the gastric pouch may further comprise the step of determining avolume of the distal balloon. The step of determining a size variable ofthe gastric pouch may comprise the step of determining an approximatelength of the gastric pouch.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows an embodiment of a catheter for measuring the size of agastric pouch;

FIG. 2 shows a close-up view of the embodiment of FIG. 1;

FIG. 3 shows a close-up view of another embodiment of a catheter formeasuring the size of a gastric pouch;

FIG. 4 a shows another embodiment of a catheter within a gastric pouchcreated by a Roux-en-Y Gastric Bypass procedure;

FIG. 4 b shows the embodiment of FIG. 4 a with its distal balloonaxially extended;

FIG. 5 shows the embodiment of FIGS. 4 a and 4 b within a gastric pouchformed by an AGB band;

FIG. 6 shows another embodiment of a catheter used to size thegastric-intestinal anastomosis; and

FIG. 7 shows an embodiment of a system for measuring the size of agastric pouch.

DETAILED DESCRIPTION

Various embodiments of devices, methods, and systems for measuring thesize of a gastric pouch are disclosed herein. It will be appreciated bythose of skill in the art that the following detailed description of thedisclosed embodiments is merely exemplary in nature and is not intendedto limit the scope of the appended claims.

FIGS. 1 and 2 show an exemplary embodiment of a catheter for measuringthe size of a gastric pouch. Catheter 100 comprises an outer elongatetube 110, having a proximal end 113 and a distal end 117, and an innerelongate tube 120, having a proximal end 123 and a distal end 127. Innerelongate tube 120 is disposed within outer elongate tube 110 such thatinner elongate tube 120 is capable of sliding within, and therefore inrelation to, outer elongate tube 110. Outer elongate tube 110 is hollowso that inner elongate tube 120 may fit within outer elongate tube 110.Inner elongate tube 120 is shown in FIGS. 1 and 2 as a solidshaft—without a hollow center—but other catheter embodiments may includean inner elongate tube that is hollow.

Catheter 100 includes a proximal balloon 130 that surrounds a portion ofouter elongate tube 110 near the distal end 117 of outer elongate tube110. As shown in the exemplary embodiment in FIG. 2, proximal balloon130 has a first end 133 and a second end 137, each of which is attachedto outer elongate tube 110. As is discussed in more detail below,proximal balloon 130 is used to identify and locate the lower esophagealsphincter at the gastroesophageal junction. Proximal balloon 130 issized for locating the lower esophageal sphincter, but other embodimentsmay include proximal balloons that vary slightly in length, based on thecircumstances. A person of ordinary skill in the art will understand,based upon this disclosure, the proper length of the proximal balloon tobe used.

Proximal balloon 130 is made from commonly known materials in the art,such as polyurethane, silicone, or any other suitable material. It ismade from enough material that it can expand circumferentially so that,as is explained in more detail below, any increase in intra-balloonpressure during expansion is due to the body wall surrounding theballoon rather than the tension of the balloon itself.

Catheter 100 also includes a distal balloon 140 that surrounds a portionof outer elongate tube 110 that is distal to proximal balloon 130.Distal balloon 140 has a first end 143 that is attached to outerelongate tube 110 and a second end 147 that is attached to innerelongate tube 120. Consequently, distal balloon 140 is axiallyadjustable so that it can be elongated or shortened, as desired, bysliding inner elongate tube 120 within outer inner elongate tube 110.Distal balloon 140 is elongated by sliding inner elongate tube 120 sothat distal end 127 of inner elongate tube 120 extends past distal end117 of outer elongate tube 110. Distal balloon 140 increases in lengthas distal end 127 of inner elongate tube 120 extends further past distalend 117 of outer elongate tube 110. Distal balloon 140 then decreases inlength as distal end 127 of inner elongate tube 120 is moved closer todistal end 117 of outer elongate tube 110 until distal end 127 of innerelongate tube 120 is aligned with distal end 117 of outer elongate tube110.

Distal balloon 140 is generally about three centimeters in lengthinitially and may be axially extended to approximately four or fivecentimeters in length. It is made from commonly known non-conductivematerials in the art, such as polyurethane, silicone, or any othersuitable non-conductive material, and is made from sufficient materialthat it can expand circumferentially as well as axially. Indeed, distalballoon 140 may be made from enough excess material that, as isexplained in more detail below, any increase in intra-balloon pressureduring balloon expansion is due to the body wall surrounding the balloonrather than the balloon itself.

Attached to the portion of outer elongate tube 110 that is surrounded bydistal balloon 140 are two excitation electrodes 150. Specifically, eachof excitation electrodes 150 has a proximal end that is capable ofattachment to a power source (not shown), such as a battery, and adistal end that is located on outer elongate tube 110 distally to firstend 143 of distal balloon 140.

Also attached to outer elongate tube 110, between excitation electrodes150, are three detection electrodes 160, spaced approximately onecentimeter apart. Each of detection electrodes 160 has a proximal endthat is capable of attachment to a processor or processing system (notshown), such as a personal computer, and a distal end that is located onouter elongate tube 110 between excitation electrodes 150. Excitationelectrodes 150 are configured to emit a measured electrical charge intothe inside of distal balloon 140, while detection electrodes 160 detectthe amount of the charge that travels through a fluid within distalballoon 140. As explained in more detail below, a processing systemcalculates the change in electrical charge to determine the conductancethrough the inside of distal balloon 140 at any given location in theballoon. Although catheter 100 is shown as having three detectionelectrodes 160, other catheter embodiments may have as few as one or twodetection electrodes, or as many as four or more detection electrodes.In addition, although detection electrodes 160 are positionedapproximately one centimeter apart, the distance between the detectionelectrodes on other catheter embodiments may vary.

Catheter 100 also comprises first pressure transducer 170 and secondpressure transducer 180. First pressure transducer 170 is attached tothe portion of outer elongate tube 110 that is surrounded by proximalballoon 130. It is therefore capable of detecting the pressure,including changes in pressure, within proximal balloon 130. Secondpressure transducer 180 is attached to the portion of elongate tube 120that is surrounded by distal balloon 140. It is therefore capable ofdetecting the pressure, including changes in pressure, within distalballoon 140.

Proximal balloon 130 and distal balloon 140 are extendedcircumferentially by inflation with fluid. Catheter 100 further includesa first fluid passageway 190 that extends from a fluid inlet or source(not shown) to the portion of outer elongate tube 110 surrounded byproximal balloon 130. First fluid passageway 190 is designed forinjecting fluid, which may comprise saline solution or some othersuitable fluid, into proximal balloon 130. Proximal balloon 130 distendsas it fills with fluid, until proximal balloon 130 expands to fill thespace within the gastric pouch or other cavity.

Likewise, catheter 100 also includes a second fluid passageway 200 thatextends from a fluid inlet or source (not shown) to the portion of outerelongate tube 110 surrounded by distal balloon 140. Second fluidpassageway 200 is designed for injecting fluid, which may comprisesaline solution or some other suitable conductive fluid, into distalballoon 140. Distal balloon 140 distends as it fills with fluid, untildistal balloon 140 expands to fill the space within the gastric pouch orother cavity in which it is disposed.

Inner elongate tube 120 includes several gradations 210 at or nearproximal end 123 of inner elongate tube 120. Gradations 210 are markingspositioned on inner elongate tube 120 two millimeters apart, but thegradations of other embodiments may be spaced apart any suitablepredetermined distance (e.g., one millimeter, three millimeters, fourmillimeters, five millimeters, or one-sixteenth of an inch). Thegradations help the practitioner determine the axial length of thedistal balloon when the distal end of the catheter has been insertedinto the body, and they therefore help the practitioner determine thelength of the gastric pouch. Indeed, the practitioner may adjust thelength of the distal balloon using the gradations for accuracy.

In the embodiment shown in FIG. 2, inner elongate tube 120 fits snuglywithin outer elongate tube 110. Although the practitioner can easilyslide inner elongate tube 120 back and forth within outer elongate tube110, inner elongate tube 120 does not inadvertently slide within outerelongate tube 110 because friction holds the two tubes together. Thearrangement is also leak-proof such that the fluid remains in the lumenof the balloon.

In some catheter embodiments, however, the inner elongate tube and outerelongate tube are engaged and held stationary to one another not merelydue to friction, but also by a latch and notch engagement. As shown inFIG. 3, catheter 300 includes outer elongate tube 310 and inner elongatetube 320, which includes gradations 330. Gradations 330 comprise notches340 on inner elongate tube 320, and outer elongate tube 310 has a latch350 at the proximal end of outer elongate tube 310 that is configured toengage each of notches 340 such that inner elongate tube 320 and outerelongate tube 310 are reversibly fastened to each other. Specifically,latch 350 is somewhat flexible to bend when latch 350 is not alignedwith one of notches 340; however, latch 350 extends to engage one ofnotches 340 when a notch is aligned with latch 350. This engagementholds inner elongate tube 320 in place (with respect to outer elongatetube 310) until the practitioner purposefully slides inner elongate tube320 by exerting sufficient force on inner elongate tube 320 to causelatch 350 to bend and release its engagement with one of notches 340.Thus, the engagement of the latch and notch is released, allowingretraction or further extension of the distal balloon.

Although catheter 300 is shown with a notch and latch engagement system,any other means for holding the inner and outer elongate tubes in theirrelative positions may be used. Indeed, as discussed above, merefriction may be sufficient to hold the two tubes in place with respectto each other.

Referring now to FIGS. 4 a and 4 b, catheter 400 is shown being used tomeasure the size of a patient's gastric pouch after the patient hasundergone a Roux-en-Y bypass procedure. Catheter 400 comprises an outerelongate tube 420 and an inner elongate tube 430 disposed within outerelongate tube 420. Attached to outer elongate tube 420 is proximalballoon 440 and the first end 453 of distal balloon 450. The second end457 of distal balloon 450 is attached to distal end 433 of innerelongate tube 430. Therefore, as explained with respect to distalballoon 140 of catheter 100, the length of distal balloon 450 may beelongated or shortened by sliding inner elongate tube 430 in relation toouter elongate tube 420.

Catheter 400 further comprises two excitation electrodes 460 positionedon outer elongate tube 420 and four detection electrodes 470 positionedon outer elongate tube 420 between excitation electrodes 460. All ofexcitation electrodes 460 and detection electrodes 470 are positioned onouter elongate tube 420 within distal balloon 450. Also attached toouter elongate tube 420 within distal balloon 450 is a first pressuretransducer (not shown). Second pressure transducer (not shown) isattached to outer elongate tube 420 within proximal balloon 440.

Under general anesthesia, sterilized catheter 400 is introduced intoesophagus 410 and advanced to gastric pouch 490, which is formed byclosure of the stomach 500 using staples 510. As shown in FIGS. 4 a and4 b, the lower portion of the patient's jejunum 520 is attached togastric pouch 490, thereby forming anastomoses 530.

To properly locate distal balloon 450 within gastric pouch 490, thepractitioner locates gastroesophageal junction 540 using proximalballoon 440. Positioning proximal balloon 440 within gastroesophagealjunction 540 properly positions distal balloon 450 within gastric pouch490 for measuring the size of gastric pouch 490.

Gastroesophageal junction 540 may be located (through a process commonlycalled manometry) by positioning proximal balloon 440 at a location ator near gastroesophageal junction 540, then injecting fluid intoproximal balloon 440 to extend proximal balloon 440 circumferentially.As proximal balloon 440 expands circumferentially, the practitioner willmonitor the pressure in proximal balloon 440 using readings from thesecond pressure transducer. Based on these readings, the practitionercan effectively locate gastroesophageal junction 540 because the loweresophageal sphincter at the junction—being a muscle—causes a more rapidrise in pressure upon balloon inflation than does the esophageal tissueor stomach tissue surrounding the junction 540. Therefore, through atrial-and-error process of inflating the proximal balloon and readingthe consequent intra-balloon pressures, the practitioner can effectivelylocate the gastroesophageal junction, thereby locating the gastricpouch. Distal balloon 450 remains deflated during positioning ofcatheter 400.

Once catheter 400 is in proper position, and therefore distal balloon450 is located within gastric pouch 490, as shown in FIG. 4 a, distalballoon 450 is adjusted axially to a desired balloon length, usuallybased on the size of gastric pouch 490. For example, as shown in FIG. 4b, distal balloon 450 has been extended axially to the wall of gastricpouch 490 by the practitioner sliding inner elongate tube 430 withinouter elongate tube 420. In other words, inner elongate tube 430 hasbeen pushed forward so that distal end 433 of inner elongate tube 430extends past the distal end of outer elongate tube 420, therebyelongating distal balloon 450.

The practitioner may adjust distal balloon 450 axially to a desiredballoon length by sliding inner elongate tube 430 within outer elongatetube 420 until one of gradations 435 on inner elongate tube 430 isaligned with the proximal end of outer elongate tube 420. Alternatively,with respect to catheter embodiments having a notch and latch mechanism,such as catheter 100 discussed above, the practitioner may adjust thedistal balloon axially to a desired balloon length by sliding the innerelongate tube within the outer elongate tube until one of the gradationson the inner elongate tube is engaged by a latch on the proximal end ofthe outer elongate tube, thereby reversibly fastening the inner elongatetube and the outer elongate tube.

In some cases, the distal balloon may have to be shortened for propermeasuring of gastric pouch size. In such cases, the practitioner mayshorten the distal balloon axially by sliding the inner elongate tubewithin the outer elongate tube. Specifically, the practitioner couldpull back on the inner elongate tube so that the distal end of the innerelongate tube is drawn toward the distal end of the outer elongate tube,thereby shortening the distal balloon. The practitioner may adjust thedistal balloon axially to a desired balloon length by sliding the innerelongate tube within the outer elongate tube until one of the gradationson the inner elongate tube is aligned with the proximal end of the outerelongate tube. Alternatively, with respect to catheter embodimentshaving a notch and latch mechanism, such as catheter 100 discussedabove, the practitioner may adjust the distal balloon axially to adesired balloon length by sliding the inner elongate tube within theouter elongate tube until one of the gradations on the inner elongatetube is engaged by a latch on the proximal end of the outer elongatetube, thereby reversibly fastening the inner elongate tube and the outerelongate tube.

Referring again to FIGS. 4 a and 4 b, after the size of distal balloon450 is adjusted axially, fluid is injected into distal balloon 450 toextend distal balloon 450 circumferentially. As explained with respectto proximal balloon 440 above, as fluid fills distal balloon 450, theballoon will distend circumferentially to fill the space within gastricpouch 490. As explained below, saline solution may be used as the fluid,injected into distal balloon 450. Although other conductive fluids maybe used with the catheter, potentially toxic fluids should be avoided.

Using catheter 400, the practitioner can determine a number of sizevariables of gastric pouch 490 (e.g., approximate length,cross-sectional area, volume). Tension and compliances may also bedetermined. First, the practitioner can determine the approximate lengthof gastric pouch 490 by referencing gradations 435 on inner elongatetube 430. For example, if the catheter gradations are set one millimeterapart, the practitioner can determine how many millimeters the distalballoon has been extended beyond its initial length.

Second, the practitioner can determine an approximate cross-sectionalarea of gastric pouch 490, often at a number of different locationswithin the pouch. To determine cross-sectional area, electricalimpedance (or conductance) is measured within distal balloon 450 usingexcitation electrodes 460 and detection electrodes 470. Suchmeasurements are described in detail in Kassab et al., System and Methodfor Measuring Cross Sectional Areas and Pressure Gradients in LuminalOrgans (Publ. No. US 2004/0230131 A1), which is incorporated herein byreference. In short, the cross-sectional area is estimated frommeasurements of the electrical impedance inside the distal balloon usingtwo or more electrodes according to Ohm's law. The voltage differencebetween the detection electrodes depends on the magnitude of the current(I) multiplied by the distance (L) between the detection electrodes anddivided by the conductivity (C) of the fluid and the cross-sectionalarea (CSA) of the balloon. Since the current (I), the distance (L), andthe conductivity (C) normally can be regarded as calibration constants,an inverse relationship exists between the voltage difference and thecross-sectional area as shown:

${CSA} = \frac{GL}{C}$

where G is conductance expressed as the ratio of current to voltage(I/ΔV). In other words, the voltage drop along each detection electrodeis measured and converted into a cross-sectional area via a calibration.

The cross-sectional area determination is relatively accurate because anon-conductive material is used for the distal balloon, inhibiting lossof electric current from the fluid within the balloon. When the distalballoon is distended to fill the gastric pouch in which it is placed(and therefore match the shape of the gastric pouch), thecross-sectional area of the distal balloon matches the cross-sectionalarea of the gastric pouch itself. Thus, determining a cross-sectionalarea of a portion of the distal balloon leads to a determination of thecross-sectional area of a portion of the gastric pouch.

Depending on the number of detection electrodes on the catheter beingused, the practitioner can determine the cross-sectional area of thegastric pouch at more than one location, thereby increasing the accuracyof certain size determinations. For example, as shown in FIGS. 4 a and 4b, catheter 400 includes four detection electrodes 470. Thus, becausethe cross-sectional area may be determined at each of the detectionelectrodes, the practitioner using catheter 400 can determine thecross-sectional area of the gastric pouch at four locations withoutmoving the catheter. As is discussed below, using four differentcross-sectional areas generally provides for a more accurate gastricpouch volume determination as compared to the use of fewercross-sectional areas.

Third, the practitioner can determine the approximate volume of gastricpouch 490. Pouch volume can be determined by multiplying the length ofgastric pouch 490 by the average cross-sectional area of gastric pouch490. Consequently, the volume determination will generally be moreaccurate if the number of cross-sectional area determinations areincreased. The following formula is used:

$V = {L^{*}\frac{1}{N}{\sum\limits_{i = 1}^{N}{CSA}_{i}}}$

where V is the volume of the pouch, L is the length of the pouch, N isthe number of detection electrodes (and therefore the number ofdifferent cross-sectional area determinations), and CSA is thecross-sectional area. If the cross-sectional area varies significantlydue to the non-uniform geometry of the pouch such that the meancross-sectional area is not accurate, the following formula may be used:

$V = {\sum\limits_{i = 1}^{N}{L_{i}{CSA}_{i}}}$

Finally, each of these size variables of gastric pouch 490 can bedetermined when gastric pouch 490 is in different states. Two of themost important states for clinical applications are when gastric pouch490 is relatively empty, which shows the pouch's resting size, and whengastric pouch 490 is full, which shows the pouch's maximum capacity. Thepractitioner can determine the relative state of gastric pouch 490 usingthe pressure within distal balloon 450, as determined by the firstpressure transducer. Thus, determining a size variable of the gastricpouch often comprises determining a pressure inside the distal balloon.

To determine a size variable of gastric pouch 490 at its resting size,distal balloon 450 should be extended to fill gastric pouch 490, butshould not be extended so much that the balloon itself expands the wallsof the gastric pouch. As the practitioner injects fluid into distalballoon 450, the practitioner references the intra-balloon pressuredetermined by the first pressure transducer. Gastric pouch 490 isconsidered at its resting size just prior to an increase inintra-balloon pressure during balloon expansion.

To determine a size variable of gastric pouch 490 at its maximumcapacity size, distal balloon 450 is extended beyond the pouch's restingsize. Based on determination of the intra-balloon pressure, thepractitioner can determine when distal balloon 450 has enlarged thegastric pouch 490 to its maximum capacity. As distal balloon 450 isfilled past the pouch resting size, the walls of gastric pouch 490 exertforce on distal balloon 450, thereby causing a relatively steadilyincreasing intra-balloon pressure. The pouch is considered to be at itsmaximum capacity when the pressure no longer steadily increases, butinstead plateaus.

Referring now to FIG. 5, there is shown catheter 400 being used to sizea gastric band 590. Thus, instead of being placed in gastric pouch 490,which was formed by staples 510, as shown in FIG. 4 a, FIG. 5 showsdistal balloon 450 being placed to size a gastric pouch formed viaconstriction by gastric band 590.

Referring now to FIG. 6, catheter 600 is similar to catheter 400,discussed above. However, catheter 600 includes outer elongate tube 610that comprises flexible portion 615 near distal end 617 of outerelongate tube 610. As shown, flexible portion 615 is capable of beingbent into a curve so that the practitioner can measure the size ofanastomoses 620 between gastric pouch 630 and lower portion of jejunum640. Thus, embodiments disclosed herein may be used to measure the sizeof gastric pouches, as well as anastomoses and other gastric lumens.Indeed, as used herein, the term “gastric pouch” may refer to a gastricpouch formed by sutures, staples, or a band, a gastric/intestinalanastomoses, or any other gastric lumen suitable for sizing inaccordance with the embodiments disclosed herein.

Catheter 600 further comprises an inner elongate tube 650. Innerelongate tube 650 is flexible so that it is capable of sliding withinflexible portion 615 when flexible portion 615 is bent into a curve.

Although catheter 600 includes outer elongate tube 610 having flexibleportion 615, other embodiments of catheters similar to catheter 600 haveouter elongate tubes that, instead of having a flexible portion, mayhave a curved portion similar to flexible portion 615 when flexibleportion 615 is bent into a curve. In those embodiments, the innerelongate tube is flexible so that the inner elongate tube is capable ofsliding within the curved portion of the outer elongate curve.

Referring now to FIG. 7, there is shown system 700 for measuring thesize of a gastric pouch or other gastric lumen. System 700 comprisescatheter 710 comprising an outer elongate tube 720, an inner elongatetube 730 disposed within outer elongate tube 720, a proximal balloon 740attached to outer elongate tube 720, a distal balloon 750 having a firstend 753 attached to outer elongate tube 720 and a second end 757attached to inner elongate tube 730, three detection electrodes 760positioned on outer elongate tube 720 between two excitation electrodes770, and a pressure transducer 780 positioned on outer elongate tube720.

System 700 further comprises a first processor 790 operatively connectedto detection electrodes 760. First processor 790 comprises a computercapable of collecting conductance data (i.e., impedance data) anddetermining various size variables, in accordance with the presentdisclosure. System 700 also comprises a power source 800, which isoperatively connected to excitation electrodes 770.

First processor 790 is also operatively connected to pressure transducer780 and is capable of collecting pressure data generated by pressuretransducer 780. First processor 790 displays pressure data,conductance/impedance data, and various size variables via a graphicaldisplay screen or other output device 810. Alternatively, in someembodiments, the first processor is not operatively connected to thepressure transducer. Instead, those systems comprise a second processorthat is operatively connected to the pressure transducer such that thesecond processor is capable of collecting pressure data.

System 700 further comprises a fluid source 820 operatively connected tothe catheter such that a fluid from fluid source 820 can be injectedinto proximal balloon 740 or into distal balloon 750. As shown in FIG.7, fluid source 820 comprises a syringe or pump.

The various embodiments of devices, systems, and methods that aredisclosed herein may be used to determine various size variables withrespect to existing pouches or for use in creating new pouches. Theembodiments should enable practitioners to standardize new proceduresand to correlate pouch size with other clinical parameters to determineclinical outcomes and prognoses.

While various embodiments of devices, systems, and methods for sizing ofgastric pouches have been described in considerable detail herein, theembodiments are merely offered by way of non-limiting examples of theinvention described herein. Many variations and modifications of theembodiments described herein will be apparent to one of ordinary skillin the art in light of this disclosure. It will therefore be understoodby those skilled in the art that various changes and modifications maybe made, and equivalents may be substituted for elements thereof,without departing from the scope of the invention. Indeed, thisdisclosure is not intended to be exhaustive or to limit the scope of theinvention. The scope of the invention is to be defined by the appendedclaims, and by their equivalents.

Further, in describing representative embodiments, the disclosure mayhave presented a method and/or process as a particular sequence ofsteps. However, to the extent that the method or process does not relyon the particular order of steps set forth herein, the method or processshould not be limited to the particular sequence of steps described. Asone of ordinary skill in the art would appreciate, other sequences ofsteps may be possible. Therefore, the particular order of the stepsdisclosed herein should not be construed as limitations on the claims.In addition, the claims directed to a method and/or process should notbe limited to the performance of their steps in the order written, andone skilled in the art can readily appreciate that the sequences may bevaried and still remain within the spirit and scope of the presentinvention.

It is therefore intended that the invention will include, and thisdescription and the appended claims will encompass, all modificationsand changes apparent to those of ordinary skill in the art based on thisdisclosure.

1. A method for measuring the size of a gastric pouch, the methodcomprising the steps of: introducing a catheter into an esophagus, thecatheter comprising an outer elongate tube, an inner elongate tubedisposed within the outer elongate tube, a proximal balloon attached tothe outer elongate tube, a distal balloon having a first end attached tothe outer elongate tube and a second end attached to the inner elongatetube, at least two detection electrodes positioned on the outer elongatetube between at least two excitation electrodes, and a pressuretransducer positioned on the outer elongate tube; locating thegastroesophageal junction using the proximal balloon; adjusting thedistal balloon axially to a desired balloon length; injecting a fluidinto the distal balloon to extend the distal balloon circumferentially;and determining a size variable of the gastric pouch.
 2. The method ofclaim 1, wherein the step of locating the gastroesophageal junctionusing the proximal balloon comprises the steps of positioning theproximal balloon at a location at or near the gastroesophageal junction,injecting fluid into the proximal balloon to extend the proximal ballooncircumferentially, and measuring a pressure inside the proximal balloon.3. The method of claim 1, wherein the step of adjusting the distalballoon axially to a desired balloon length comprises the step ofextending the distal balloon axially by sliding the inner elongate tubewithin the outer elongate tube.
 4. The method of claim 3, wherein thestep of adjusting the distal balloon axially to a desired balloon lengthfurther comprises the step of sliding the inner elongate tube within theouter elongate tube until a gradation on the inner elongate tube isaligned with the proximal end of the outer elongate tube.
 5. The methodof claim 3, wherein the step of adjusting the distal balloon axially toa desired balloon length further comprises the step of sliding the innerelongate tube within the outer elongate tube until a gradation on theinner elongate tube is engaged by a latch on the proximal end of theouter elongate tube, such that the inner elongate tube and the outerelongate tube are reversibly fastened.
 6. The method of claim 1, whereinthe step of adjusting the distal balloon axially to a desired balloonlength comprises the step of shortening the distal balloon axially bysliding the inner elongate tube within the outer elongate tube.
 7. Themethod of claim 6, wherein the step of adjusting the distal balloonaxially to a desired balloon length further comprises the step ofsliding the inner elongate tube within the outer elongate tube until agradation on the inner elongate tube is aligned with the proximal end ofthe outer elongate tube.
 8. The method of claim 6, wherein the step ofadjusting the distal balloon axially to a desired balloon length furthercomprises the step of sliding the inner elongate tube within the outerelongate tube until a gradation on the inner elongate tube is engaged bya latch on the proximal end of the outer elongate tube, such that theinner elongate tube and the outer elongate tube are reversibly fastened.9. The method of claim 1, wherein the fluid injected into the distalballoon comprises saline solution.
 10. The method of claim 1, whereinthe step of determining a size variable of the gastric pouch comprisesthe step of determining a pressure inside the distal balloon.
 11. Themethod of claim 1, wherein the step of determining a size variable ofthe gastric pouch comprises the step of determining a cross-sectionalarea of at least a portion of the distal balloon.
 12. The method ofclaim 11, wherein the step of determining a size variable of the gastricpouch further comprises the step of determining a volume of the distalballoon.
 13. The method of claim 1, wherein the step of determining asize variable of the gastric pouch comprises the step of determining anapproximate length of the gastric pouch.
 14. A method for measuring thesize of a gastric pouch, the method comprising the steps of: introducinga catheter into an esophagus, the catheter comprising an outer elongatetube, an inner elongate tube disposed within the outer elongate tube, aproximal balloon attached to the outer elongate tube, a distal balloonhaving a first end attached to the outer elongate tube and a second endattached to the inner elongate tube, a detector comprising electrodespositioned on the outer elongate tube, and a pressure transducerpositioned on the outer elongate tube; locating the gastroesophagealjunction using the proximal balloon; injecting a fluid into the distalballoon to extend the distal balloon circumferentially; and determininga size variable of the gastric pouch using the catheter.
 15. The methodof claim 14, wherein the step of injecting the fluid further comprisesthe step of adjusting the distal balloon axially to a desired balloonlength prior to injecting the fluid.
 16. The method of claim 14, whereinthe step of determining a size variable of the gastric pouch comprisesthe step of determining a pressure inside the distal balloon.
 17. Themethod of claim 14, wherein the step of determining a size variable ofthe gastric pouch comprises the step of determining a cross-sectionalarea of at least a portion of the distal balloon using the detector. 18.The method of claim 14, wherein the step of determining a size variableof the gastric pouch comprises the step of determining a volume of thedistal balloon using the detector, wherein the detector comprises atleast two detection electrodes positioned on the outer elongate tubebetween at least two excitation electrodes.
 19. A method for measuringthe size of a gastric pouch, the method comprising the steps of:introducing a catheter into an esophagus, the catheter comprising anouter elongate tube, an inner elongate tube disposed within the outerelongate tube, a proximal balloon attached to the outer elongate tube, adistal balloon having a first end attached to the outer elongate tubeand a second end attached to the inner elongate tube, a detectorcomprising at least two detection electrodes positioned on the outerelongate tube between at least two excitation electrodes, and a pressuretransducer positioned on the outer elongate tube; locating thegastroesophageal junction using the proximal balloon by positioning theproximal balloon at a location at or near the gastroesophageal junction,injecting fluid into the proximal balloon to extend the proximal ballooncircumferentially, and measuring a pressure inside the proximal balloon;adjusting the distal balloon axially to a desired balloon length;injecting a fluid into the distal balloon to extend the distal ballooncircumferentially; and determining a size variable of the gastric pouchusing at least one of a balloon pressure, a balloon cross-sectionalarea, or a balloon volume, using one or more of the detector and/or thepressure transducer.
 20. The method of claim 19, wherein the step ofadjusting the distal balloon axially to a desired balloon length isperformed by extending or shortening the distal balloon axially bysliding the inner elongate tube within the outer elongate tube.